Derecho in Progress? Damaging Wind Threat in VA/NC later this Evening/Tonight?


An ‘unregionally’ and anomalously strong elevated mixed layer is present across the Carolinas and Mid-Atlantic, with 700-500 mb lapse rates on the order of 8-9 C/km.  The combination of very steep mid-level lapse rates, temperatures in the lower 100’s, and dewpoints in the mid/upper 60s to lower 70s (highest to the north in VA) is resulting in extreme instability over the Mid-Atlantic, with MLCAPE values as high as 4000-5000 J/kg.  Additionally, extreme DCAPE values (1500-2000 J/kg) are present across the same region.  Convection upstream over the central MS river valley this morning began organizing along outflow by early afternoon, evolving into a pronounced bow echo which has progressed into IN/OH as of 20Z.  Given the environment in place it is likely that the bow echo currently racing into OH at 60+ mph will be long-lived, producing violent straight-line winds across several states.  As the bow progressed through IN into OH, numerous observations reported wind gusts of 50-60 knots, with at least two observations (Fort Wayne/IN and Dayton/OH) reporting wind gusts in excess of 70 knots.

METAR KFWA 291854Z 27055G79KT
METAR KDAY 292026Z 35042G71KT

Will the MCS maintain itself over the southern Appalachians and produce damaging winds in VA/NC later this evening/tonight?  Given the extreme and highly anomalous thermodynamic environment in place across the region, I think the odds are good that it will.  It looks like the best threat for damaging (and potentially extreme) winds will be in central and northern VA, however, the damaging wind threat would likely extend southward along the southern periphery of the MCS into southern VA and northern NC, as well.

Brandon Vincent
NWS Raleigh, NC

About bvincentnws

Meteorologist National Weather Service 2003 - Current
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2 Responses to Derecho in Progress? Damaging Wind Threat in VA/NC later this Evening/Tonight?

  1. Jonathan Blaes @ WFO RAH says:

    Derecho confirmed.

  2. Pingback: Late June 2012 Derecho | CIMMSE

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